J/AJ/158/77 Candidates and members of the Pisces-Eridanus stream (Curtis+, 2019)
TESS reveals that the nearby Pisces-Eridanus stellar stream is only 120 Myr old.
Curtis J.L., Agueros M.A., Mamajek E.E., Wright J.T., Cummings J.D.
<Astron. J., 158, 77-77 (2019)>
=2019AJ....158...77C 2019AJ....158...77C (SIMBAD/NED BibCode)
ADC_Keywords: Populations, stellar ; Stars, nearby ; Effective temperatures ;
Photometry ; Optical ; Radial velocities ; Stars, distances
Keywords: open clusters and associations: individual (Pisces-Eridanus Stream,
Pleiades, Praesepe, NGC 6811) - stars: evolution -
stars: individual: (HD 1160 B, TOI 451) - stars: rotation
Abstract:
Pisces-Eridanus (Psc-Eri), a nearby (d∼80-226 pc) stellar stream stretching
across ∼120° of the sky, was recently discovered with Gaia data.
The stream was claimed to be ∼1 Gyr old, which would make it an exceptional
discovery for stellar astrophysics, as star clusters of that age are rare
and tend to be distant, limiting their utility as benchmark samples.
We test this old age for Psc-Eri in two ways. First, we compare the
rotation periods for 101 low-mass members (measured using time-series
photometry from the Transiting Exoplanet Survey Satellite) to those of
well-studied open clusters. Second, we identify 34 new high-mass candidate
members, including the notable stars λ Tauri (an Algol-type
eclipsing binary) and HD 1160 (host to a directly imaged object near
the hydrogen-burning limit). We conduct an isochronal analysis of the
color-magnitude data for these highest-mass members, again comparing our
results to those for open clusters. Both analyses show that the stream
has an age consistent with that of the Pleiades, i.e., ∼120 Myr. This makes
the Psc-Eri stream an exciting source of young benchmarkable stars and,
potentially, exoplanets located in a more diffuse environment that is
distinct from that of the Pleiades and of other dense star clusters.
Description:
TESS (Ricker et al. 2015JATIS...1a4003R 2015JATIS...1a4003R) is currently conducting a
year-long photometric monitoring campaign of the southern sky. TESS
scans the sky in a series of sectors for ∼27 days at a time. Full-frame
images (FFI) are recorded with a 30 m cadence. As of writing, FFI data
for the first five sectors have been released to the Mikulski Archive
for Space Telescopes (MAST). Meingast et al. (2019, J/A+A/622/L13)
published a list of 256 candidate members of the Psc-Eri stream. We used
the Web TESS Viewing Tool (WTV) to identify stars observed during
Sectors 1-5, and we found 154 with data from at least one sector. We
downloaded 20x20 pixel cutouts of the FFI images centered on each target
using the TESScut tool hosted at MAST (Brasseur et al.
2019ascl.soft05007B). Next, we used the IDL procedure aper.pro from
the IDL Astronomy User's Library (Landsman 1993ASPC...52..246L 1993ASPC...52..246L) to perform
aperture photometry on all epochs in the image stack produced by TESScut.
We used a circular aperture with a three-pixel radius (∼1' based on TESS's
∼21" pixel scale).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 84 101 Rotation periods for Meingast et al. (2019,
J/A+A/622/L13) members of the Psc-Eri stream
table3.dat 101 34 Candidate massive members of the Psc-Eri stream
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS) (Sullivan+, 2015)
J/A+A/622/L13 : Stellar stream in Gaia DR2 discovery (Meingast+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/101] Sequential running number, sorted
by GBP-GRP
5 A1 --- f_Seq [a] Source flag (1)
7- 25 I19 --- Source Gaia DR2 identifier
27- 28 I2 h RAh Hour of Right Ascension (ICRS) (G1)
30- 31 I2 min RAm Minute of Right Ascension (ICRS) (G1)
33- 36 F4.1 s RAs Second of Right Ascension (ICRS) (G1)
38 A1 --- DE- Sign of the Declination (ICRS)(G1)
39- 40 I2 deg DEd Degree of Declination (ICRS) (G1)
42- 43 I2 arcmin DEm Arcminute of Declination (ICRS) (G1)
45- 48 F4.1 arcsec DEs Arcsecond of Declination (ICRS) (G1)
50- 54 F5.3 mag GBP-GRP [0.432/1.852] Gaia DR2 GBP-GRP color (G1)
56- 59 I4 K Teff [3956/7187] Surface effective temperature (G1)
61- 66 F6.3 mag Gmag [8.562/13.375] Gaia DR2 G band magnitude (G1)
68- 72 F5.3 mag GMag [2.802/8.099] Absolute G mag,
MG=G-5*log10(100/π) (G1)
74- 78 F5.2 d Prot [0.45/12.22] Rotation period derived from TESS
full-frame images (FFI) data
80- 84 A5 --- Note Note (2)
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Note (1): Source flag as follows:
a = This star has been identified as a planet candidate host by TESS (TOI 451,
TIC 257605131), and appears to show two sets of transits with periods of
9.19 d and 16.36 d, which await validation.
Note (2): The notes indicate if a star:
Conv. = Converged on the slow sequence;
Slow = Is slower than the converged sequence;
Rapid = Is more rapid than the converged sequence;
LM = Has a lower mass than the converged sequence limit;
Warm = Is too warm to efficiently spin down.
Regarding the "Slow" stars, five stars appear to rotate more slowly than the
bulk of the sample. Blending is not a concern for these stars (i.e., none have
bright neighbors in DR2 within 1.5 arcmin), their spot-modulated light curves
show unambiguous periodicity, and they do not appear to be binaries according
to their photometry, RV errors (σ<2 km/s), and kinematics. It is unclear
to us why they are outliers.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/34] Sequential running number, sorted by GMag
4- 22 I19 --- Source Gaia DR2 identifier
24- 25 I2 h RAh Hour of Right Ascension (ICRS, epoch 2015.5) (G1)
27- 28 I2 min RAm Minute of Right Ascension (ICRS, epoch 2015.5)
(G1)
30- 34 F5.2 s RAs Second of Right Ascension (ICRS, epoch 2015.5)
(G1)
36 A1 --- DE- Sign of the Declination (G1)
37- 38 I2 deg DEd Degree of Declination (ICRS, epoch 2015.5) (G1)
40- 41 I2 arcmin DEm Arcminute of Declination (ICRS, epoch 2015.5)
(G1)
43- 46 F4.1 arcsec DEs Arcsecond of Declination (ICRS, epoch 2015.5)
(G1)
48- 53 F6.3 mag GBP-GRP [-0.193/0.495] Gaia DR2 GBP-GRP color (G1)
55- 59 F5.3 mag Gmag [3.387/8.999] Gaia DR2 G band magnitude (G1)
61- 66 F6.3 mag GMag [-2.039/2.927] Absolute G mag (G1)
68- 71 F4.1 km/s RV [5/19.9]? Radial velocity obtained from SIMBAD
73- 75 F3.1 km/s dV [1.3/4.7]? Absolute deviation of UVW velocities
from the stream's median value Δv
77- 79 F3.1 mas/yr dmu [0.3/9.3] Minimum difference in proper motion
relative to the nearest neighbor Δµ (1)
82- 85 F4.1 pc dr [0.1/18.7] Physical distance to nearest neighbor
Δr (1)
87- 99 A13 --- Name Common alias
101 A1 --- Note Note on particular stars from SIMBAD (2)
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Note (1): In the Meingast et al. (2019, J/A+A/622/L13) list.
Note (2): Note as follows:
a = Algol-type EB;
b = Be star;
c = α2 CVn variable;
d = Peculiar composition;
e = Binary or multiple star;
f = HD 1160 has two low-mass companions (Nielsen et al. 2012ApJ...750...53N 2012ApJ...750...53N) -
HD 1160C is an M3.5 dwarf (Gaia DR2 2741090498159705216), and HD 1160B is
a brown dwarf candidate with an estimated mass of 39-166 MJup
(Maire et al. 2016A&A...587A..56M 2016A&A...587A..56M), 35-90 MJup, and 70-90 MJup
(Garcia et al. 2017ApJ...834..162G 2017ApJ...834..162G), depending on the age of the host
star. Interpolating the 125±15 Myr evolutionary models from
Baraffe et al. (2015A&A...577A..42B 2015A&A...577A..42B) at the Garcia et al.
(2017ApJ...834..162G 2017ApJ...834..162G) temperature (Teff=3050±50 K) and luminosity,
corrected with the Gaia DR2 (Cat. I/345) parallax
(log L/L☉=-2.59±0.05 dex), we infer a mass
MB=0.117±0.01 M☉ (∼123 MJup). This is greater than the
hydrogen-burning limit and indicates that HD 1160B is probably a
very-low-mass star and not a brown dwarf.
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Global notes:
Note (G1): Coordinates (in ICRS), GBP-GRP, Teff, Gmag are from Gaia DR2
(Cat. I/345); MG=G-5*log10(100/plx) using plx from Gaia DR2.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 30-Sep-2019